. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. INSECTS 229. Spiracle with its trachea} removed from an insect; s, spiracle. Three times natural size. Photographed by Davison. Tracheae.—The trachese divide and subdivide like branches of a tree so that all the body cavity is reached by their fine endings. Some even pass outward into the veins of the wings. Each of these tubes contains air. The blood of an insect does not cir- culate through a system of closed blood tubes as in man, but in- stead it more or less completely fills that part
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. INSECTS 229. Spiracle with its trachea} removed from an insect; s, spiracle. Three times natural size. Photographed by Davison. Tracheae.—The trachese divide and subdivide like branches of a tree so that all the body cavity is reached by their fine endings. Some even pass outward into the veins of the wings. Each of these tubes contains air. The blood of an insect does not cir- culate through a system of closed blood tubes as in man, but in- stead it more or less completely fills that part of the body cavity which is not filled with other organs. A heart (a hollow mus- cular organ containing several openings, situated on the dorsal side of the insect) causes move- ment of the blood inside the body cavity in much the same way that a rubber bulb would circu- late water if squeezed inside a pail of water, so that sooner or later the blood comes in contact with the oxygen passed in through the trachese. Muscular activity. — Insects have the most powerful muscles of any animals of their size. Relatively, an enormous amount of energy is released during the jumping or flying of a grasshopper. The tracheae pass directly into the muscles, where oxidation takes place when the muscles are exercised. Thus oxygen is taken directly to the parts of the body where it is to be used. The body temperature of the grasshopper is slightly higher than the sur- rounding air. Why? Mouth Parts. — Feed a grasshopper with a blade of grass. Note how the animal holds the grass. What appendages aro used ? Note the upper lip and lower lips, the latter biparted. The dark brown Jaws (mandibles) may be seen underneath. Below them are a pair of smaller pointed parts, the maxillse, to which are attached a pair of jointed palps. Note also that palps are attached to the lower lip. Food Taking and Blood Making. — The plant food taken by the grasshopper is held in place in the mouth by means of
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